Returns landing changeset, or if that doesn't exist returns the tip

        """

        cs = self.get_changeset(self.landing_rev) or self.get_changeset()

        return cs

    def update_changeset_cache(self, cs_cache=None):

        """

        Update cache of last changeset for repository, keys should be::

            short_id

            raw_id

            revision

            message

            date

            author

        :param cs_cache:

        """

        from rhodecode.lib.vcs.backends.base import BaseChangeset

        if cs_cache is None:

            cs_cache = self.get_changeset()

        if isinstance(cs_cache, BaseChangeset):

            cs_cache = cs_cache.__json__()

            _default = datetime.datetime.fromtimestamp(0)

            last_change = cs_cache.get('date') or self.last_change or _default

            log.debug('updated repo %s with new cs cache %s' % (self, cs_cache))

            self.updated_on = last_change

            self.changeset_cache = cs_cache

            Session().add(self)

            Session().commit()

    @property

    def tip(self):

        return self.get_changeset('tip')

    @property

    def author(self):

        return self.tip.author

    @property

    def last_change(self):

        return self.scm_instance.last_change

    def get_comments(self, revisions=None):

        """

        Returns comments for this repository grouped by revisions

        :param revisions: filter query by revisions only

        """

        cmts = ChangesetComment.query()\

            .filter(ChangesetComment.repo == self)

        if revisions:

            cmts = cmts.filter(ChangesetComment.revision.in_(revisions))

        grouped = defaultdict(list)